Dry concentrating apparatus



J. H. w. HOFFMAN 2,798,607 DRY CONCENTRATING APPARATUS- July 9, 1957 3 Sheets-Sheet 1 Filed March 27; 1953 July 9, 1957 J. H. w. HOFFMAN 1 2,798,607

DRY GONCENTRATING APPARATUS I s Sheets-Sheet 2 Filed March 27, 1953 y 9, .57 J. H. w. HOFFMAN 2,798,607

' may cbucawmnmc APPARATUS 3 Sheets-Sheet 3 Filed March 27, 1953 United Stte 2,7d8fih7 Patented July" 9, 1957 John H. W. Hoffman, Chicago, EL, assignor to Charles H. Fox, Winnetha, Philip S. Dreyfus, farms W. Casey, and John H. W. Hoffman, all of Chicago, lith, trustees Application March 27, 1953, Serial No. 345,169 s Claims. till. 2tE9-467) This invention relates to improvements in dry concentrating apparatus and it consists of the matters herein described and more particularly pointed out in the appended claims.

One of the objects of the present invention is to provide apparatus for operating upon sized and graded material, such as the yield from mines and the like, to separate the waste particles from the valuable particles therein, without requiring the use of water which is often difiicult to obtain in the vicinity of the yield.

Another object of the invention is to provide apparatus of simple construction for effecting a separation of mixed particles of various sizes within certain limits, according to the specific gravity of such particles.

A further object of the invention is to provide apparatus of this kind which will operate efliciently on several kinds of material and which affords a greater and cleaner yield of valuable particles, thereby reducing concentrating costs.

Also it is an object of the invention to provide apparatus of this kind which operates, upon a continuously flowing stream of material in a manner effecting separation of Waste and valuable particles from each other.

Again it is an object of the invention to provide apparatus of this kind which will not become clogged or obstructed by dust, dirt and the like and therefore requires but little if any servicing and lay-up time therefor.

Furthermore, it is an object of the invention to provide apparatus of this kind wherein the waste particles of n1aterial are discharged laterally from the apparatus as they are separated from the valuable particles and whereby the separating action increases in efficiency as the flow stream of material decreases in depth toward the discharge end of the apparatus.

The above mentioned objects of the invention, together with others, will more fully appear as the specification proceeds.

In the drawings:

Fig. 1 is a view in side elevation apparatus embodying the preferred form of the invention.

Fig. 2 is a top plan view of the apparatus appearing in Fig. l, with the material feed hopper appearing in horizontal section.

Fig. 3 is a vertical longitudinal section through a part of the improved apparatus as taken on the line 33 and on a scale enlarged over that of Fig. 2.

Fig. 4 is a top plan view of the parts appearing in Fig. 3.

Figs. 5 and 6 are detail vertical sectional views through portions of the air permeable deck of the apparatus as taken on the lines 5-5 and 6-6 respectively, on Fig. 4 and on a scale enlarged thereover.

Figs. 7 and 8 are transverse vertical sectional views through parts of the apparatus as taken on the lines 7-7 and 8--8 respectively on Fig. 1 and on a scale enlarged thereover.

Fig. 9 is a perspective view of a certain air control cap embodied in the apparatus and which will be described in more detail later.

of a dry concentrating In general the improved dry concentrating apparatus is intended to operate upon graded and sized material such as the yield from a mine and containing waste matter and valuable matter.

It includes an elongated trough which preferably has a semicylindrical cross section and it is cushion mounted for vibratory movement on a subframe. This subframe, in turn, is so mounted upon the main supporting frame of the apparatus that it, and the trough it carries, have a downward pitch or inclination from that end of the trough into which the graded and sized material is fed, toward its other end and from which the valuable matter is dis charged. The mounting of the subframe upon the main frame is such that the pitch or inclination is adjustable angularly so that the apparatus is capable of handling different kinds of materials.

The trough, which carries a number of electric vibrators, is provided below its top edge with an air permeable, concentrating deck or table which extends the full length thereof. A deck made in sections of vitrified Carborundum blocks well serves the purposes as it has a multicellular structure affording a complete diflusion of air under pressure from below and as it is uniform throughout in texture there are no blow-through or dead spots in its active top surfaces.

The trough is provided below the deck with transverse partitions, which divide the same into compartments covered by associated parts of the deck so as to convert said compartments into substantially leak-proof air chambers. In the bottom of and extending the length of the trough is a manifold to which air under pressure is fed from a suitable motor driven pump, preferably supported on the main frame of the apparatus below the feed end trough and to which it is connected by a flexible conduit. The manifold has an upwardly opening branch in each air chamber and each branch supports a cap with a laterally opening outlet and associated with each cap is a valve operable from one side of the trough, whereby the volume of air under pressure entering each air chamber may be regulated.

In the operation of the apparatus, due to the vibration of the inclined trough, the valuable particles of the material being operated upon work toward the active surface of the deck while the lighter waste particles seek a level above that of the valuable particles and are floated by the air passing up through the deck or table. As the mass of material flows longitudinaly along the deck or table, the lighter waste particles are diverted laterally toward the sides of the trough to discharge out through openings provided therefor in the sides of the trough about flush with the active face of the deck or table. This lateral diversion of the waste particles is effected by means of sets of blades that are disposed angularly inwardly and forwardly of the deck at spaced intervals above the active surface of the deck or table. These blades decrease in height toward the discharge end of the trough in accordance with the depth of the flow stream of the material operated upon, which also decreases in depth and increases in valuable particle content toward said discharge end of the trough.

The active surface of that part of the bed or table, to ward the discharge end thereof, is provided with flow groove arrangement whereby the valuable particles are reduced in flow stream width for a better separation of remaining waste particles therefrom prior to the discharge of such valuable particles from the apparatus.

Ref rring now in detail to that embodiment of the invention illustrated in the drawings, the apparatus includes a rigid main frame indicated as a whole at 1E, which frame is longer than it is wide. it is composed of laterally spaced, horizontally disposed, side rails l e-d6, supported at spaced intervals upon the top ends of angle bar legs 17--17 rising from longitudinal bottom members 18, which legs are suitably connected together by cross rails 19, one of which best appears in Fig. 7. The side rails 16 are in the form of angle bars with their horizontal flange directed outwardly and with their vertical flanges directed downwardly.

The apparatus also includes a longitudinally extending subframe disposed above the top of the main frame and this sub-frame is indicated as a whole by the numeral 20 in said Fig. 7. It includes laterally spaced, longitudinally extending side rails 21 in the form of angle bars, the horizontal flanges of which extend outwardly and are disposed above the like flanges of the rails 16. The vertical flanges of the rails 21 extend downwardly and are disposed inwardly of the like flanges of the rails 16.

While the rails 21 of the subframe extend longitudinally of and are supported upon the like rails of the main frame, they are inclined downwardly at a low variable angle relative to the like rails of the main frame, from that end into which the material to be concentrated is fed to the apparatus, toward that end from which the valuable particles separated from the waste particles of said material are discharged from the apparatus.

Each side rail of the subframe is so mounted upon the like rail of the main frame below the same that the inclination of the subframe may be varied or adjusted and thereby adapt the apparatus for concentrating several materials of several different specific gravities. One way to so mount the rails 21 for this adjustment in inclination is to provide longitudinally spaced jack screws 22 that are threaded through and extend upwardly from the hori zontal flanges of the side rails 16 of the main frame and have a swivelled engagement at the top end with the horizontal flanges of the side rails of the subframe. Nuts 23 are disposed on each screw above and below the flange of the rail 16 for holding the screws in that position providing the desired inclination for the subframe. Thus, While the subframe may be adjusted in inclination relative to the main frame, it is rigidly supported from the main frame by said screws.

The subframe serves to support a longitudinally extending trough-like body 25 in a manner whereby said body is mounted for vibratory movement relative to the subframe. This body is herein shown as being of a semicylindrical cross section, the sides of which are extended upwardly by side plates or walls as that are rigidly attached thereto. This body and its side plates are mounted on longitudinal rails 27 in the form of angle bars and the horizontal flanges of these rails face outwardly and are disposed above the like flanges of the rails 21 and the vertical flanges of said rails 247 face downwardly. Suitable vibration absorbing mounts 28 are dis posed between and operatively connect the horizontal flanges of the associated rails 21-27 together. Such mounts, each of which includes a body of rubber, may be purchased in open market as Lord mounts and applicant makes no claim to the structure thereof.

At longitudinally spaced points along the central bottom portion of said trough-like body are operatively secured a plurality of electromagnetic vibrationg mechanisms 30, which are commercial products that may be purchased in the open market. Vibrating mechanism known by the trade name as Syntrons well serve the purpose.

At each end of the trough-like body is a closure wall 31-32, the former being at the material feed end and the latter being at that end from which the valuable particles of the material operated upon are discharged.

At longitudinally spaced points of the trough are located transverse partitions 35 and 36, which appear best in Fig. 3, and which coact with the closure walls in dividing the trough into a plurality of front, intermediate and rear end air chambers 37, 38 and 39 respectively, closed at the top by an air permeable deck or table, preferably made up of front, intermediate and rear end sections 40, 41 and 42 respectively. Preferably each section is made of a multicellular material affording a complete diffusion of air from the chamber below and the elimination of blow or dead spots on the active top surface of the table or deck. Each section may be in the form of a slab-like block and as an example of a material of which to make said sections, vitrified Carborundum is mentioned. This is merely by way of illustration and not by way of limi tation because there are other materials which would also serve the purpose.

Each partition 35-36 is provided at its upper end with oppositely facing angle bars 43 and on the inner face of the upper margin of the trough-like body longitudinal angle bars 44. The angle bars 44 afford support for the side margins of the bed sections and the angle bars 43 aflord support for the end margins of said sections. Preferably a mastic filler 45 is applied between the parts mentioned to afford a tight seal so that the air chamber 3738 and 39 in the trough-like body are substantially leakproof. This filler best appears in Figs. 7 and 8. This mastic filler has such qualities that said parts are adhesively united, whereby no relative movement can occur between the trough-like body and the deck or table.

In the space between the side plates 26 and above the top or active surface of the deck, directly above the partitions 3 5-36 are transverse walls 50 and 51 respectively, each having a material passage Etta-51a in the central bottom portion thereof, and mounted on the front of each wall are vertically adjustable gates 52 and 53 respectively for controlling the effective size of the associated passage. The rear end wall 32 of the trough has a discharge opening 54 therein and on the inner face thereof is a vertically adjustable gate 55 for controlling the effective size of said opening. On the outer face of said wall 32 is a trough 56 to receive the valuable particles or concentrates of the material operated upon, which trough directs said particles into suitable containers (not shown) placed to receive the same. The parts just mentioned appear best in Fig. 3.

In the longitudinal center of the upper active face of the intermediate and rear end sections of the deck or table and extending from end to end thereof is a collecting trough or groove 60 which best appears in Figs. 3 and 4. As shown therein said groove widens or flares toward the end closure 32 and it also gradually deepens toward said end. in those parts the upper active face of these two sections, at each side of the groove 60, are diagonally extending branch or riffle grooves 60a. These branch grooves start from nothing and gradually deepen toward that end where they open the sides of the groove. These grooves are angled inwardly and toward the closure 32 of the trough-like body and are of a somewhat V shaped cross section, as best appears in Fig. 6 and one side of each groove is perpendicular to the active face of the bed or deck and the other side is inclined from the perpendicular. Thus the groove arrangement follows a herringbone pattern and by making one side of each branch groove perpendicular to the active face 'of the deck, movement of the material on the deck is facilitated in the direction of the main collecting groove 60.

On the upper active surface of each deck section are pairs of material deflecting bars 61, 62 and 63 respectively, each of which is suitably fixed in a groove in the face of the associated section as shown in Fig. 5. The front end of each pair of bars begins at the sides of the associated section and are directed inwardly toward the center of the deck to terminate at their rear ends at the partitions 35, 36 and end wall 32 respectively, as best appears in Fig. 4. The angle of inward inclination of the bars in each successive pair increases with respect to the longitudinal center of the associated bed section. Also the top edge surface of each bar in each pair decreases in height above said active surface of the deck and are the highest at the front end and lowest at the rear end, as best appears in Fig. 3. With this arrangement of deflecting bars a better separating action is atforded between the waste and the valuable particles of the material operated upon and a better lateral deflective action is afforded for the waste particles or gangue toward the side plates 26 while confining the valuable particles for a longitudinal movement along the central portion of the deck toward the discharge end 32 of the apparatus and the discharge opening 54 in said end.

In said side plates 26 are longitudinal openings 65, 66 and 67 respectively and in connection with each opening is an inclined tray 68, 69 and 70 respectively for discharging waste particles from the apparatus.

Extending longitudinally of the bottom of the trough and through the partitions 35 and 36 is a manifold 76 for air under pressure, which is suitably plugged at that end thereof that ends in the chamber 39. The other end of said manifold is disposed adjacent the end closure 31 of the trough and has connected thereto the upper end of a tube 71 that is connected at its lower end to an air pump '72, which best appears in Fig. 1. This pump is driven by a motor 73 and both the pump and its motor are engaged upon a platform 74- supported from a lower portion of the main frame. The tube 71 has a slip joint 71a therein which affords an extension and contraction in length thereof to accommodate for making adjustment of the inclination of the sub frame and trough therein relative to the main frame.

The manifold is provided in each air chamber with an upright extension 75 which carries a cap 76 at the top. This cap extends transversely of the apparatus and includes vertically spaced top and bottom walls 77-78 and having a lateral air discharge 79. The bottom wall has side grooves to receive the lateralmargin of a plate-like valve or gate 80, by which the volume and pressure of air discharged from the cap into the associated air chamber may be regulated. The gate 80 may be moved inwardly or outwardly of the cap from outside the apparatus by means of a rod 81 that is operatively connected at its inner end to the gate 80. The outer end of this rod has a knob 82 thereon for manipulating the rod inwardly or outwardly. Where the rod passes through the associated side of the trough body, said side is provided with a bushing 83 to prevent leakage of air from the associated chamber to atmosphere.

Associated with each chamber 37, 33 and 3% is a pres sure indicating gauge 85 disposed at that side of the trough opposite the side through which the rods 81 pass. This gauge is mounted on the upper end of a tube 86, the other end of which opens into one side of the associated air chamber. This tube is supported at the top by an upright 87 from the rail 20 of the sub frame and in the top end of said tube is a valve 38. By means of the gauges the pressure of the air in the chambers 37, 38 and 39 is visibly indicated and by means of the gate 80 the pressure of air in each chamber may be regulated.

At the front or feed end of the apparatus is located a hopper 90 to hold the graded and sized material to be concentrated by separating the worthless particles or gangue from the valuable ones. This hopper is provided with a gate 92 by which the feed of material from the hopper into the feed end of the apparatus may be controlled. These parts best appear in Figs. 1 and 2.

When the electric vibrators 30 are energized, they set up a high frequency, low amplitude vibration of the trough 25 and deck carried thereby, which vibration is cushioned and absorbed by the mounts 28 so that the vibration is not transferred to the sub frame. Assume now that the gate 92 for the hopper 90 is opened to that extent which affords a feed of material from the hopper upon the front or feed end of the deck or table to build up thereon a flow stream, say on theworder of an inch thick or deep, assuming the material is of such character as to the size of its constituents held by a twenty mesh screen. Assume also that air is discharged into each chamber 37, 38 and 39 respectively under about a pound of pressure below the deck, resulting in a pressure of the order of a couple of ounces at the active surface of the deck. This pressure is suificient to float the waste particles in the material, which have a lighter specific gravity, from the valuable ones, which have a heavier specific gravity. By reason of the action of the air at the active surface of the deck, in combination with the vibration of the trough and deck, together with the inclined plane of the latter, there is brought about a separation of the waste particles and the valuable particles as two groups or layers with the waste particles at the top of the material. 7

By reason of the inclination and vibration of the bed or deck, a stream of the material flows towards the dis charge end of the apparatus with the lighterwaste particles setting up an ebullition or floating action at the upper level of the flow stream and with the heavier valuables seeking the lower level on the deck. As the flow stream moves toward the gate 52, the bars 61 on the active surface of the deck of the front end section direct the material inwardly and as said material approaches the gate 52 which has been opened to the desired extent, the lighter waste particles of material flow laterally over the rear end parts of the bars, Where their height is the lowest, and then pass laterally out through the openings ed in the side plates 26.

As the material on the front section of the deck reaches the plate 52 in the wall 50, the lighter particles will pile up thereagainst to flow laterally and the heavier particles then pass under the gate and onto the active surface of the intermediate deck or bed section to be operated thereupon. The material flowing onto said intermediate section will be much richer in valuable particles and the flow stream thereof will have a depth less than that first fed to the feed section of the bed. Here the material meets another stage of separation and as the volume of the flow stream becomes less, the waste particles therein may be better separated from the valuable ones. On this section of the bed the material is acted upon for a further separation of the waste and valuable particles, and as the material approaches the gate 53 the waste particles build up thereagainst to flow laterally over the lower ends of the bars 62 to pass through the openings 66 for a discharge from the apparatus. As the material stream flows along the active surface of the intermediate section the branch grooves 60qtherein direct the heavier valuable particles into the longitudinal groove or channel 60, which particles flow toward the gate 53 which has been opened to the proper height for the passage of a predetermined depth of the stream to flow into the discharge end section. It is obvious that the flow stream of material passing under the gate into the active surface of the discharge section of the deck will be richer than the material entering upon the intermediate section of the bed. By the use of the term richer it is meant that the flow stream will have a higher percentage of valuable particles and a lower percentage of Waste particles, the richer particles usually being of greater density than the waste particles. As this flow stream approaches the gate in the end wall 32, the bars 63 direct the flow stream toward the groove 60, where said valuable particles build up in depth. By a proper setting of the gate 55 the flowstream may be held back at this point so that such waste particles as may remain therein build up as a layer on top of the layer of valuable particles in the deepest end of the groove to How or spill laterally over the lower end of the bars 63 to flow out the openings 67 for discharge from the apparatus. As the valuable particles build up in the discharge end of the groove 60, and with the gate 55 opened to the desired extent, said particles dischargethrough the opening 54 and down the tray-like chute 56 for dischargeinto a receptacle. It is obvious from the above thatthe material flow stream on the front deck section 40 receives an initial concentrating action, wherein the greatest of volumes in waste particles is separated from the remainder of the material and thus passes as a richer material to the second section. In this section the material receives another separation so that while the flow stream grows smaller in volume it is much richer when it passes onto the third section of the bed for the final separation of waste particles from the valuable ones. Thus the material discharged from the third section of the bed or deck is extremely high in yield of valuable particles of the material and will contain only a small percentage, if any, of waste particles.

The apparatus is eflicient and rapid in operation and is adjustable for concentrating materials of diiierent specific gravities.

I claim as my invention:

1. Dry concentrating apparatus embodying therein a trough-like body mounted for vibratory movement and having a downward inclination from that end into which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck supported by said trough and coacting with the same to provide an air chamber, means for imparting vibratory movement to said trough, means for supplying air under pressure to said chamber for passage up through said deck, means disposed in oprative relation to the active top surface of the deck contacting the same and rising upwardly therefrom for causing the waste particles in said material to how over the same and laterally outward for discharge through at least one side of the trough, predeterminately spaced apertured wall means transversely disposed on said active top surface of said deck dividing said deck into a predetermined number of longitudinal deck sections and restricting the movement of the material on said deck surface, a valuable particle collecting channel in said deck surface that deepens and widens toward an outlet for said material disposed at said other end 'of said trough whereat said channel terminates, said channel commencing at said wall means disposed furthest from said outlet, and arranged in alignment with each of said wall means apertures, and means disposed at said other end of the trough for controlling the discharge of the valuable particles of the material therefrom.

'2'. Dry concentrating apparatus embodying therein a trough-like body mounted for vibratory movement and having a downward inclination from that end into which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck supported in said trough and coacting with the same to provide an air chamber, means for imparting vibratory movement to said trough, means for supplying air under pressure to'said chamber, means disposed in said trough in operative relation to the active top surface of the deck contacting the same and rising upwardly therefrom for causing particles in said material to flow over the same and laterally outward for discharge through the sides of the trough, said means embodying therein sets of blades that extend angularly inward from the sides of the trough toward the longitudinal center of the deck and toward said other end of the trough, predeterminately spaced apertured wall means transversely disposed on said active top surface of said deck dividing said deck into a predetermined number of longitudinal deck sections and restricting the movement of the material on said deck surface, a valuable particle collecting channel in said deck surface that deepens and widens toward an outlet for said material disposed at said other end of said troughwhereat said channel terminates, said channel commencing at said wall means disposed furthest from said outlet and arranged in alignment with each of said wall means apertures, and means disposed at said other end of the trough for controlling the discharge of the valuable particles of material therefrom.

3. Dry concentrating apparatus embodying therein a trough-like body mounted for vibratory movement and having a downward inclination from that end into which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck supported in said trough and coacting with the same to provide an air chamber, means for imparting vibratory movement to said trough, means for supplying air under pressure to said chamber, means disposed in said trough in operative elation to the active top surface of the deck for directing the waste particles in said material laterally outward for discharge through the sides of the trough, said means embodying therein sets of blades that extend angularly inward from the sides of the trough toward the longitudinal center of the deck and toward said other end of the trough, said blades decreasing in height as they approach said other end of the trough, predeterminately spaced apertured wall means transversely disposed on said active top surface of said deck dividing said deck into a predetermined number of longitudinal deck sections and restricting the movement of the material on said deck surface, a valuable particle collecting channel in said deck surface that deepens and widens toward an outlet for said material disposed at said other end of said trough whereat said channel terminates, said channel commencing at said wall means disposed furthest from said outlet, and arranged in alignment with each of said wall means apertures, and means disposed at said other end of the trough for controlling the discharge of the valuable particles of material therefrom.

4. Dry concentrating apparatus embodying therein an elongated trough mounted for vibratory movement and having a downward inclination from that end into which the material operated is fed therethrough toward its other end from which the valuable particles in said material are discharged, longitudinally spaced partitions in said trough, an air permeable deck supported in said trough and coacting with said partitions in dividing the trough into a plurality of air chambers therein, a manifold extending longitudinally of the trough and having an upwardly directed neck in each chamber, a hood on each neck formed to discharge air therefrom in the general direction of the length of the manifold, means for controlling the air entering each hood from the associated neck, means disposed in said trough in operative relation to the active top surface of the deck for directing the waste particles in said material laterally outward for discharge through the sides of said trough, and means disposed at said other end of the trough for controlling the discharge of the valuable particles of the material therefrom.

5. In a dry concentrating apparatus the combination of a trough-like body mounted for vibratory movement and having a downward inclination from that end to which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck carried by said trough and closing the top of the same, and means operative in the vibration of the trough and extending inwardly from the sides thereof toward the center line of the deck, said means comprising bar-like members that decrease in height toward said other end of the trough, a portion of said trough at said other end of the trough having a valuable particle collecting channel in its top surface that deepens and widens toward an outlet for said material from said other end of the trough, said portion of said trough having a series of grooves in its top surface arranged in herringbone order and opening into the channel from the sides thereof.

6. In a dry concentrating apparatus the combination of a trough-like body mounted for vibratory movement and having a downward inclination from thattend to which the material operated upon is fed thereto toward its other end-from which the valuable particles in said material are discharged, an air permeable deck carried by said trough and closing the top of the same, and means operative in the vibration of the trough and extending inwardly from the sides thereof toward the center line of the deck, said means comprising bar-like members that decrease in height toward said other end of the trough, a portion of said trough at said other end of the trough having a valuable particle collecting channel in its top surface that deepens and widens toward an outlet for said material from said other end of the trough, said portion of said trough having a series of grooves in its top surface arranged in herringbone order and opening into the channel from the sides thereof, and means carried by said end of the trough and operable to control the effective area of said outlet relative to the associated end of the channel.

7. In a dry concentrating apparatus the combination of a trough-like body mounted for vibratory movement and having a downward inclination-from that end to which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck carried by said trough and closing the top of the same, a plurality of longitudinally spaced walls extending transversely of the active surface of the deck and dividing the same into a plurality of sections, means on said active surface of each section comprising a pair of material directing bars that extend longitudinally of said surface and taper inwardly toward the longitudinal center of the deck surface as a whole toward an associated transversely extending wall, the inner ends of said pairs of bars being spaced successively closer to each other as they approach an associated transverse wall, the bars in each set decreasing in height toward the associated transverse wall.

8. In a dry concentrating apparatus the combination of a trough-like body mounted for vibratory movement and having a downward inclination from that end to which the material operated upon is fed thereto toward its other end from which the valuable particles in said material are discharged, an air permeable deck carried by said trough and closing the top of the same, means providing a longitudinal groove in the central portion of the active surface of the deck, for at least a part of its length and which groove increases in depth and width toward the discharge end of the trough-like body, a plurality of longitudinally spaced walls extending transversely of the active surface of the deck and dividing the same into a plurality of sections, means on said active surface of each section comprising a pair of material directing bars that extend longitudinally of said surface and taper inwardly toward the longitudinal center of the deck surface as a whole toward an associated transversely extending wall, the inner ends of said pairs of bars being spaced successively closer to each other as they approach the as sociated transverse wall, the bars in each set decreasing in height toward the associated transverse wall.

References Cited in the file of this patent UNITED STATES PATENTS 1,068,163 Payne July 22, 1913 1,590,339 Wood June 29, 1926 1,710,521 Sutton Apr. 23, 1929 1,730,947 Raw Oct. 8, 1929 2,007,098 Peale July 2, 1935 2,155,235 Morgan Apr. 18, 1939 2,275,849 Fraser Mar. 10, 1942 

